The invention is concerned with a matter-conductive crown element for the packing of a matter-exchange column. The invention is also concerned with a matter-exchange column having crown elements of that kind.
The exchange part of such a column in which in particular an upwards flowing gas (steam) and a counter-flowing liquid are brought into contact, consists of a packing which fills the cross-section of the column out to an annular gap at the column wall. The crown elements which encircle the packing serve for the deflection of these flows of matter. The gas flow is forced into the packing by the crown elements; the gas is thereby impeded from partially flowing through along the region at the edge of the column without coming into contact with the liquid. The packing is in particular an ordered packing which brings about a distribution of the two flows of matter across the cross-section of the column.
The packing is composed, for example, of layers of undulating laminations or laminations folded in a zigzag. The laminations consist of a material like foil; the edges at the folds or ridges extend in a direction inclined with respect to the axis of the column, for example, at an angle to the axis amounting of 45.degree. or 30.degree.. The layers formed by the laminations are aligned in parallel with the axis; with respect to the slope of the edges at the folds they are arranged alternately so that open channels result which run obliquely and cross. The packing is organized in sections which differ in the orientation of the layering. Between adjacent sections the orientation changes each time through 90.degree..
Through the oblique channels in the packing, part of the liquid flows to the region at the edge. To prevent this liquid from contacting the column wall an edge gap is provided, that is, the above-mentioned annular gap. Without the edge gap a considerable part of the liquid would flow down along the column wall.
By means of the edge gap it becomes possible for the liquid arriving at the edge of the packing to be returned into the interior of the packing again through other channels. However, it cannot be avoided in practice that a certain proportion of the liquid does spill over against the column wall and thereby impair the matter-exchange process. The crown elements have the additional function of conducting the liquid back from the column wall to the packing where the liquid is subsequently led through some of the channels back into the interior of the packing.
Further examples of ordered packings which bring about a distribution of the two flows of matter across the cross-section of column, are described in the European Patents 0 070 917 and 0 069 241.
U.S. Pat. No. 4,186,159 or CH-PS 618 006 disclose a crown element for a packing which is there designated as a "collar". The description of the FIG. 8 shown there reads as follows (quotation): To the bottom parts of the built-in elements (here called portions of packing) diverter elements made as collars are fastened, which seal the annular gap between the packing body and the column wall and cause the liquid flowing down the inner wall to be conducted inwards against the underside of each built-in element. Such collars may also be arranged at various heights of the built-in elements.
One single portion of packing of the matter-exchange column may consist of one coherent built-in element; it may--especially in the case of columns of large diameter--also be composed of a number of segments. For simple mounting of the column it is necessary for the collars to be fastened to the built-in elements or segments already before installing the packing. Since the packing consists of thin-walled material, the fastening of the collars, which may be done by welding (but also by screwing or riveting) is an expensive manufacturing step.